1. Field of the Invention
The present invention pertains to a structural rod for reinforcing a structural member, such as a mass of concrete material.
2. Description of the Prior Art
It is known to reinforce concrete structures by embedding therein rods or bars which are formed of closely adherent groups of fine glass fibers bounded together into a unitary structure; these rods are used as concentrated reinforcing members in the same manner as steel rods are used. Such reinforcing element may be found and described, for example, in U.S. Pat. No. 2,425,883 issued Aug. 19, 1947 to John G. Jackson. This patent describes a method for preventing slippage of the individual fibers forming the rod relative to each other and uneven stressing of certain of the strands. The method consists in grouping the strands together by a relatively inelastic bounding medium. Also, in order to increase the bond between the cement and the fibrous reinforcing member, the latter is deformed at spaced intervals along its length. This deformation is accomplished by pressing the resin impregnated fibers together into an intimate mass. There results a rod which has embossments of square section in those deformed areas. One disadvantage of such structural rod is that the pressing operation defeats the purpose of preventing uneven stressing of the individual fibers of the rod since the resulting geometry in fact creates an uneven distribution of forces in the rod. By producing a reinforcing element which has square-shaped embossments, a shearing occurs in the cementitious material at the periphery of the rod, especially in those regions having an angulation of 90.degree.. Also the pressing operation requires a fixed station to perform such operation; this results in a repetitive sequence of stop-and-start to create embossments on the rod. If heat is required, time delay will be added to the molding process. The embossments will be of a weaker nature due to the absence of continuous fibers in such concentrated areas.
Also in the U.S. Pat. to Jackson, it is said that it is possible to have phenolic resin cured under heat after being incorporated in a concrete liquid mass which will harden before the polymer matrix. It has been found that it is impossible to cure uniformly phenolic resin after being immersed in liquid concrete due to the presence of water and humidity. Phenolic resin is sensible to water and humidity and such ambient medium results in an uneven undercured polymer matrix. Also, the presence of water and cement before polymerization of thermoset resin generates a chemical attack on the fiber-resin matrix interface resulting in a weaker strength and debonding.